Method of forming a shallow groove isolation structure

A method for manufacturing a semiconductor device, comprising the steps of:

• thermally oxidizing a circuit forming surface of a silicon substrate to form a first silicon oxide film;
• forming a silicon nitride film on said first silicon oxide film;
• forming grooves in said silicon substrate with said silicon nitride film as a masks said grooves having sidewall portions extending from the surface of the silicon substrate;
• receding said first silicon oxide film from the sidewall portions of said grooves;
• after receding said first silicon oxide film, oxidizing said grooves in a range of 0<C≦0.88t−924 in which hydrogen density in oxidation atmosphere is 6 ppm or lower, an oxygen partial pressure in air corresponding to an oxygen partial pressure ratio is C %, and oxidation temperature is t (° C.), t being equal to or greater than 1050° C.;
• after oxidizing said grooves, burying a second silicon oxide film inside of said grooves;
• after said burying step, removing said silicon nitride film formed on the circuit forming surface of said silicon substrate;
• and
• after removing said silicon nitride film, removing said first silicon oxide film formed on the circuit forming surface of said silicon substrate.